Method of and apparatus for the formation of concrete pipes



Dec. 12, 1950 GOWlNG 2,533,579

METHOD OF AND APPARATUS F OR THE FORMATION OF CONCRETE PIPES Filed July 22, 1949 4 Sheets-Sheet l INVENTOR AT OR/VEY [Vglsomfi Golding.

METHOD OF AND. APPARATUS FOR THE FORMATION OF CONCRETE PIPES Dec. 12, 1950 N E ow 2,533,579

Filed July 22, 1949 4 Sheets-Sheet 2 ZNVENTOR.

ATTORNEY NelsOngL'.

Dec. 12, 1950 N. E. GOWING 2,533,579 METHOD OF AND APPARATUS FOR THE FORMATION OF CONCRETE PIPES Filed July 22, 1949 4 Sheets-Sheet 3 5'4 4 233/ 33 E 9 I A 4 z-42 .19. 2a 0 52; C 39 I :72 [Velsbrz E. Goa/flag.

. I K BY ATTORNEY Dec. 12, 1950 N. E. GOWING 2,533,579

METHOD OF AND APPARATUS FOR THE FORMATION OF CONCRETE PIPES 4 Sheets-Sheet 4 Filed July 22, 1949 Nelson E.

ATTORNEY Patented Dec. 12, 1 950 METHOD OF AND APPARATUS FOR THE FORMATION OF CONCRETE PIPES Nelson E. Gowing, Wombourne, Wolverhampton, England Application July 22, 1949, Serial No. 106,166 In Great Britain December 24, 1948 This invention relates to a process and apparatus for the formation of concrete pipes by moulding, and relates to that type of process wherein the pipe is formed from concrete of a stiff consistency (for example having a minimum consistency factor of 250 as recorded on the Wigmore Consistometer) within a vertical mould by utilising a rotary piston or packer having packer elements, the said piston moving vertically upwardly from the bottom of the mould whilst rotating, with the concrete mix fed on to its head, the centrifugal force throwing the concrete mix outwardly, so that a shell is built up against the mould which is consolidated by the rotating piston.

The apparatus or machine utilised for carrying out the above process is of the type consisting of a suitable supporting structure or framework having means for holding the mould and locating same in axial alignment with the piston,

the piston being carried and rotated by a vertical shaft, the apparatus including means for moving said shaft axially, i, e. up and down, whereby the piston during the pipe forming operation traverses within the mould from the bottom to the top, the piston, its shaft and parts moving therewith being counterbalanced. The pipe or shell is formed by pouring the concrete on to the top or head of the piston, the centrifugal force throwing the mix outwardly where it is built up into a shell and consolidated by the piston and packer elements, and after formation when the piston and shaft are clear of the mould the said mould is removed from the apparatus, with the ,formed and green pipe therein.

With the process above set out, the consolidating action of the piston when forming the pipe results in liquid or fat forming on the inner wall or bore, and this formation, coupled with the helical path of travel of the piston, causes ridges or irregularities to form on the said wall. It is customary for pipes manufactured by this process to be finished off as well as possible by means of smoothing or pallet knives immediately after pipe formation when the mould has been removed from'the machine, but even with this finishing, it is difficult to produce a perfectly even or unscored bore, or a pipe of the standard normally associated with pipes manufactured by the centrifugal spinning process. This latter process however cannot produce pipes so cheaply as they can be produced by a moulding process of theabove type.

- The primary object of the present invention is to provide an improved process and apparatus for the formation of concrete pipes by moulding 17 Claims.

wherein the bore of the pipe, after the formation of said pipe, is smoothed mechanically and. adequately, the smoothing action taking place whilst the mould is still in its position in thepipe-forming machine.

A further object of the invention is to provide v:

an improved process and apparatus for the formation of concrete pipes wherein the inner wall can be lined with a suitable material which enables extremely smooth and if necessary, substantially impervious pipes to be made as compared with pipes manufactured by normal moulding methods, thus producing a moulded pipe that is adequately consolidated and which will pass the standard accepted air pressure test.

Another object is to provide a process and apparatus which will enable smooth bore pipes to be manufactured at a cost which compares favourably with pipes as at present produced by existing moulding apparatus.

- A further object is to provide an apparatus which is easily-operated and of robust construction.

Yet another object of the invention is to provide an apparatus which can be utilised for the production within limits of pipes of various lengths and diameters, whilst a further object to provide an apparatus in which metal or other reinfmement can be set up in the mould to beembedded within the formed shell."

In order that a clear understanding of the invention may be obtained a preferred form of machine for forming pipes in accordance with the invention will now be described with refer-- ence to the accompanying drawing in which: I

Figure 5 is a side view of the piston partly in section, and

Figure 6 is a plan view of the turntable and its supporting tray.

Referring to the drawings, the framework consists of suitable uprights and cross bracing members of H-, angle section or like strip indicated generally by the reference numeral 1.: The main supporting member for the assembly consisting of the piston ll, its shaft l2 and its driving motor l3, consists of a vertical pillar l4 which is disposed centrally of the frame and is of H-cross section. The said assembly is sum-- tric motor [3 at he rear of the pillar l4, and a mounting l5 for the lower end of the piston shaft l2 and its outer casing I2a at the front of said pillar both carried on a suitable supporting structure I6, the motor driving the shaft through pulley and beltf drive indicated. generally l1. The supporting structure has rollers I8 which run on suitable vertical parts of the frame, the whole structure being mounted in such a way that side to side movement is absent or reduced to a minimum.

The piston II is mounted on the upper end of the shaft, which shaft is of such a length that it can traverse vertically the length of the appropriate mould. It will be noted that the piston is on the top of its shaft, in co'ntradistinctlon to the usual arrangement in which the pis-- shaftlll; each endof which carries a flanged drum .2 I, around which is a cable 22 (one at each sideof the frame) connected to the assembly. Azcounterbalance weight v23 running in a vertical guide 23a is provided at each side and the cable ateach sideextends from the weight over and around the drum 2| on the cross-shaft end down to, a suitable part of the assembly where it is.

anchored. This is shown clearly in Fig. 2 With.

this arrangement overdrive is prevented as either. thecounterbalance weight or thepiston assembly will rest on the ground or bottom members of the frame when the limit of move,- ment is reached in either direction thereby loosenmg, the cables around their shaft pulleys.

The. motor l9 drives throughsprockets 24, 25

and chain 26 a lay shaft 21 mounted in suitable journalsacross the topof the frame andnear. tqthe front said shaft having two sprockets 28,

29, which sprockets drive through chains 30,.

3|, respectivelysprockets 32, 33 free on the crossshaft at the rear of the lay shaft 21. A sliding dog member 34 is keyed on to the said crossshaft between the two sprockets, thereon, which member is toothed at each end whilst the face ing bosses 35, 36, of the sprockets 32, 33, respectively are similarly formed so that a sliding dog clutch arrangement is provided. When the dog member 34 is movedalong the shaft to engage the dogs of one of the sprockets 32, 33, the gear ratio between the motor and cross-shaft is different from the ratio when the dog member 34 is; moved to engage the dogs of the other of said sprockets.

Thechange speed is conveniently effected automatically upon the reversal of the directionoi, rotation of the motor. Carried on and driven by, one end of the lay shaft 21 is one element 31 of a friction drive, the other element 38 being co-axial therewith and pressedthereto by a spring 39. The second e1ement-38 is coupled by-an arm 40 the head of which is formed as a -collar 4| on the shaft and .between'the element and:linkage 42 to the dog member, and them-'- ransement is such that when the .direc ion of.

motor rotation is reversed the friction between the members results in the collar 4| turning through an angle sufficient to rock the arm causing the dog member to slide on its shaft and engage the other sprocket. The ratio between the drive for the downward movement of the piston assembly and the upward movement thereof is preferably 3-'l so that the downward rate of travel of the piston is three times the upward "rate.

The mould support consists of a lower or floor plate 43 having pins 44 for location in dowel holes in the bottom ring of a conventional two part mould shell, and an upper supporting tray 45 with a mould retaining ring 46 on its underside, saidtray being mounted so as to be capable of vertical movement to allow for the insertion and removal of a mould and also if necessary, the'utilisation of moulds of different heights. A circular plate 41 is mounted for rotation on the tray and also to serve as the support for an upper former as later. described. The upper support ingtray is guided at each side by vertical mem.-

bers 48 which run on the vertical front members of the supporting frame If], Counterbalanced bars 59, 59,v mounted on a cross axle-49 areconnected by the coupling rods, 50, 50, to the underside of the tray 45. The cranked lever 5| projects from the front of the machine and is operatively connected to the axle: 49, whereby on raising the lever the tray is raised through,

the rods 50 and bars 59, and on lowering the lever the tray is lowered. The arrangement is such. that the tray tends to rise. The tray 45 has a central hole 52 with the mould locating means 45 on its underside.

Suitable stops are provided to retain the-tray against upward movement during the pipe form,- ing operation. Said stops: comprise -a pair of.

thereby enabling the tray to rise. and so. allow for theinsertion .or removalofthe mould. Con.-

veniently each stop bar 53 is in two parts coupled together by a nut and bolt and slots, whereby.

the overall length can. be adjusted.

The piston is illustrated in Figs. 4 and5, and consists of a main body H having a central hollow boss 60, the lower edge of theskirt of which body is chamfered as at 6|, The wall is preferably built up from metal strip 62 whichpistonerown. Each said element consists. of.

blade pivoted on a vertical pivot axle or spindle 64, the lower end of each axle being received in a recess 64a whilst the upper end offeach;

spindle is received in a recess 64b, in a hori;

direction of travel, shown by-the arrow inFig.

4) to rear, and the said blades are coupled to;

gether through a toggle mechanism anda verti;

cal actuating rod 65 passing through the. centre of the piston and its driving shaft and freely rotatable with respect thereto. The upstanding part of the rod 65 is formed as a plate 66 and on each side a bar 51 is pivoted, each bar 61 being connected at its outer end by a rigid curved rod 68, to a blade adjacent the pivot spindle of said blade. As shown in Fig. l'the lower end of the actuating rod 65 projects from the lower end of the piston driving shaft and is supported through a suitable bearing at this end. A yoke 69 connects a collar ll! around the end of said rod to a lever ll pivoted at 12 so that the depression of the lever end raises the actuating rod (which rod is free to turn) whilst the raising of said lever end lowers the actuating rod. The lever end is arranged to engage adjustable stops the one 13 at the limit or downward movement of the piston, the other 14 at the limit of upward movement.

When the piston is rising after the lever II has contacted the stop 13, the packer blades 63, 63, by their rear edges, overhang the piston wall an appropriate amount, e. g. about one eighth part of an inch. The two bars 61 aforesaid are aligned or past centre, toggle fashion in this position but when the piston reaches its limit of upward travel, the lever end meets the stop 14 thereby raising the actuating rod 65. Owing to the toggle linkage this results in the turning of the rod through a small angle and the packer elements or blades through the bars 61 and the curved rods 68, turn on their pivot spindle 64 an amount sumcient to bring their rear edges within the diameter of the piston. When the piston is at its limit of downward travel, the actuating rod is lowered thereby turning the blades to their projectin position.

The socket end of the pipe is formed at the top, the lower part of the mould having a ring or other suitable member therein to form the male end of the pipe. The plate 41 is if necessary, arranged to receive therein a cylindrical former the outer surface of which will decide the shape of the inner wall of the pipe at the mouth, the mix being forced between the former and the mould when the piston nears the top of its travel. Any suitable form of socket may be utilised and the former is not illustrated in the drawings. It is preferred however, to effect rotation of the socket former in a contrary direction to the direction of rotation of the piston and for this purpose, the plate 41 is mounted as a turntable having a channel section circumferential wall 15 supported by suitable rollers 16. The former is engaged in the turntable for example by means of projecting bars on the former which engage under lugs 83 on the plate 41, and the turntable is driven by an electric motor Tl beneath the table, the drive being through a telescopic shaft 58 and roller 19 mounted eccentrically. The said roller 19 is controlled by the hand lever 80, through linkage 8| beneath the table, whereby the roller can be brought to engage the wall 15, or drawn therefrom, a thrust roller 82 being provided. It will be understood that if it is necessary to rotate the plate 41, such rotation is necessary only when the piston approaches the plate. The turntable is prevented from movement in the same direction as the piston by means of the radial rack bars 84 and pawl 85.

As stated above the shape of the former will depend upon the required shape of the mouth and preferably, for forming a spigot and socket pipe, the machine employs a former and the apparatus as described in our co-pending application Serial No. 106,167 filed July 22, 1949.

1 It will be understood that for forming the pipe, with the mould in position and the piston at its lowermost position, the drive to rotate the piston is started up (a speed of between 200 and 300 R. P. M. being suitable), and the mix is fed into the mould, the drive for raising the piston being started. The mix due to centrifugal force is flung outwardly against the mould. The packer blades by their rear parts overhang the piston slightly, and their height is such that the concrete is built up into a shell in the mould.

to be consolidated by the following piston. When the piston approaches the former member at the top, said member is rotated in the direction opposite to the direction of rotation of the piston. The piston will finally leave the mould and former and when the head is clear of the former, the packer blades are automatically retracted.

The direction of rotation of the motor assembly drive is now reversed and it returns at a faster axial speed through the pipe. This return movement causes the inner pipe surface to be smoothed and the tapering skirt of the piston assists in this operation.

If it is desired to line a pipe, after the return movement, the process is repeated and a suitable, lining composition is fed on to the top of the piston. This composition may consist of sand and cement with or without other fillers such as powdered glass, carbon or other suitable material. It will be understood that after lining, the piston must be returned, the return movement finishing off and smoothing the lined bore.

The second or lining operation, with the throwing on to the piston crown of the lining material, resuits in the packer blades wiping the material into the surface and alsofurther coinpressing the concrete. In this way, an extremely hard inner surface can be obtained. It will .be understood that the aggregate used in the mix includes a large proportion of fairly large stone chips, which tend to produce a rough and badly pitted inner surface. The lining operation in particular produces an inner surface in which. there are no large cavities, and further the 1in-.. ing material can be selected so that the pipe is for all normal uses, impervious.

It is a further feature of the invention that metal reinforcement can be set up in the mould, as the packer blades do not overhang for the full mould diameter.

It will be seen that the smoothing operation isv effected whilst the formed pipe is still in its mould which is in position in the machine, the piston, with its packer blades retracted being passed through the formed shell at the completion-of:

the forming operation. As no substantial con-- solidation of the concrete is necessary, the axial. speed is greater during smoothing than during forming, and said speed must be such that no undue burning of the bore or lining takes place.

Whilst a preferred mode of and apparatus forv carrying the invention into effect has been described and illustrated, it is to be understood that alterations or modifications may be made without departing from the spirit of the invention as claimed in the appended claims.

Iclaim:

1. A process of forming concrete pipes by moulding and involving the use of a vertical mould within which a co-axial vertically moving rotating piston travels, said piston being mounted on the upper end of its driving shaft and havin packing blades at its top which project beyond the piston wall, said process consisting in moving the rotating piston from the bottom of the mould tolthe top whilst the concre'temix-iis poured .on;

to .1 d f ith piston, there to :be flung 'Ollt-r wardly and formedand. consolidated into the pipe shell :by the packer blades and piston,.retracting :said :blades after-the shell-formation to with in thecliameter of the piston, and returningthe said piston .at aspeed higher than the speed of the upward moving piston .with the blades iretracted through the formed shell, thespeed of travel v on the're'turn being such that the piston serves tosmoothandlclean up the inner-wall, without burning.

2. -A :process of forming concrete pipes by moulding and involving the use of a vertical mould within which a co-axial vertically moving rotating piston travels, :said piston being mounted on the upper end of its-driving shaft and having packing blades at-its top which projeot beyond the piston wall, said process consisting-in moving the rotating-piston from the bottom of the mould to the top whilstthe concrete mix is poured on to the head of the piston, there to be flung outwardly and formed and consolidated into the pipe shell by the packer blades andpiston, retracting said blades after the shell formation-to within the diameter of the piston, then moving said piston upwardly whilst rotating and whilst feeding a granular-lining material on to the head of said piston and finally in returning the rotating piston through the bore with the blades retracted at an axial speed to finally smooth off the lined bore.

3, tConcretepipe making machine comprising a supporting structure, a vertical shaft carried by said structure, a piston on the upper end of said shaft, means for rotating said piston, means for moving said piston carried by said shaft axially through a verticalmould supported by the structure, saidaxial movement comprising an upward movement from the bottom of the mould to the top'for pipe formation and a return downward movement after formation, packer blades on said piston, means for maintaining said blades protuberant of the piston wall when said piston travels from .the bottom of the mould upwardly for pipe formation, automatic means retracting said blades to Within the piston diameter and operative'when said piston rises above the top of the mould, said retracting means maintaining said blades within the piston diameter during the piston return from the top of the mould downwardly, the axial speed on return being a a faster rate than the axial pip forming speed.

4. Concrete pipe niahing machine comprising a supp rting structure, a vertical shaft carried by said structure, a piston on the upper end of said shaft, means for rotating said piston, means moving said piston and shaft axially through a vertical mould supported by the structure, said axialmovement comprising upward movement from the bottom of the mould to the top for pipe formation and a return downward cleaning and smoothing movement after formation, with the return movementat an axial speed faster than the axial speed during pipe formation, packer elements on said piston, and automatic means retracting the packer elements and operative on the piston rising above the-top of the mould.

5. Concrete pipe making machine comprising a ;supporting structure, a vertical shaft carried by said structure, a piston on the upper end of said shaft, means for rotating said piston, means tor-moving said piston and shaft axially through a vertical mould supported by the structure, said exist-movementcomprisingan unwardme eme i movement an amount sufficient forthe rearverticai edges of said bladestooverhangthe pist'onf wall, said movement in the-other direction-pivot ing the blades through the linkage-for downward piston movement to retract said rear edges to within the piston diameter.

6. Concrete 'pipe'making machine comprising a supporting structure, a vertical shaft carried by said structure, a piston on the upper end ofsaid shaft, means for rotating said piston, means" for moving said-piston and shaft axiallythrcugh a vertical mould supported by the structure, said axial movement comprisin upwardmovement' fromthebottom of the mould to the top for pipe formation and a return downward cleaning," and smcothing movementafter formation, with "the return movement atan axial speed faster than the axial speed during pipe formation, packer eiements on said piston, said elements comprising two blades each mounted on a vertical pivot on the piston head and oppositely 0n a CO 1110111 diameter, a vertical rod, concentric within the shaft, a linkage between said rod and the blades, means for moving said rod axially in either direction, said movement in one direction pivoting the blades through linkage for upward pistr movement ananic-unt su l caledges of said blades to overhan the piston said movement in the other direction. pive t bl des hrough the link e for downward piston movement to retract said rear edges to withinthe .piston diameter, the said means'ior,

moving the rod com sing a con ling between the lower end of said rod and membersmuu f tcfl' an h upporting tr t re, which memberslar located to ,moi 'e the rod through the couplingwhen the piston and shaft assembly ,reaches limit of travelin either-direction. fl

'7. Concrete pipe making machine comprising; a supporting structuraa vertical'shaft carried byv said structure, a piston on the upper-end ofsaid shaft, means .i'or rotating said piston, means for moving said piston and shaft axially through ,a-

vertical mould supported by the structure, said axial movement comprising an upward movement. fromithe bottom of the mould to the topfor pipe formation and a return downward cleaning and smoothing movement after formation, with the, return movement at an axial speed faster than. the axial speed during pipe formation, packer elements on said piston, said elements ;C0m;pri &-

' ing two blades each mounted on a vertical pivot on the pistonhead and oppositely on a comm-an diameter, avertical rod concentric within the shaft, a linkage between said rod and the blades, means for moving said rod axiallyin-either direction, said movement in one direction pivoting-theblades through the linkage for upward piston. movement an amount suiiicient for the rear ver-; tical edges of said blades to overhang the piston: wall, said movement in the other direction pivot.- ingthe blades through the lineage fordownward piston moveiiz'ntto retract said rear edges to within the piston diameter, the said means for moving the rod comprisinga pivoted arm carried by the piston and shaft assembly a pivoted coupling between one end of said arm and the lower end of the rod and abutments carried by the supporting structure and spaced apart, one ofsaid abutments engaging. the other end of the arm when the piston assembly reaches its limit of travel in either direction to move said rod axially.

8. Concrete pipe making machine comprising a supporting structure, a vertical supporting pillar substantially centrally of said structure, a carrier platform mounted to travel vertically on and supported by said structure, a vertical shaft mounted at its lower end for rotation on said carrier platform, a piston on the upper end of said shaft, retractable packer blade elements on said piston, an electric motor mounted on said carrier platform and coupled to the shaft for the rotation thereof, means for moving the carrier platform vertically on the supporting pillar, means for supporting a mould in axial alignment with the shaft and piston assembly, means for maintaining the packer blade elements protuberant of the piston wall when said piston assembly travels upwardly from the bottom of said mould for pipe formation, means for retracting said blades to within the piston diameter after pipe formation, the means for moving the carrier to return the piston after pipe forming operating to return said piston at a faster axial speed than during pipe formation.

9. Concrete pipe making machine comprising a supporting structure, a vertical supporting i.

pillar substantially centrally of said structure, a carrier platform mounted to travel vertically on and supported by said structure, a vertical shaft mounted at its lower end for rotation on said carrier platform, a piston on the upper end of said shaft, retractable packer blade elements on said piston, an electric motor mounted on said carrier platform and coupled to the shaft for the rotation thereof, means for moving the carrier platform vertically on the supporting pillar, said means comprising a motor driven shaft carried across the top, a counterweighted cable drive from said shaft to the platform, means for supporting a mould in axial alignment with the shaft and piston assembly, means for maintain ing the packer blade elements protuberant of the piston wall when said piston assembly travels upwardly from the bottom of said mould for pipe formation, means for retracting said blades to within the piston diameter after pipe formation, the means for moving the carrier to return the piston after pipe forming operation to return said piston at a faster axial speed than during pipe formation.

10. Concrete pipe making machine comprising a supporting structure, a vertical supporting pi1- lar substantially centrally of said structure, a carrier platform mounted to travel vertically on and supported by said structure, a vertical shaft mounted at its lower end for rotation on said carrier platform, a piston on the upper end of said shaft, retractable packer blade elements on said piston, an electric motor mounted on said carrier platform and coupled to the shaft for the rotation thereof, means for moving the carrier platform vertically on the supporting pillar, said means comprising a motor driven shaft carried across the top, a counterweighted cable drive from said shaft to the platform, means for supporting a mould in axial alignment with the vertical shaft and piston'assembly, a vertical rod concentric within the vertical shaft, linkage-between said rod and the blades, means for moving "said rod axially in either direction, said move-- ment in one direction pivoting the blades through the linkage for upward piston movement "an amount sufficient for the rear vertical v edges of said blades to overhang the piston wall,

said movement in the other direction pivoting the blades through the linkage for downward piston movement to'retract said rear edges to shaft driving through sprockets and chains two sprockets freely mounted on the cable driving shaft, either of which free sprockets can be connected to the said cable driving shaft by means of a clutch, the sizes of the sprockets being such that for the same motor speed of rotation, the cable driving shaft rotates at a faster rate when the clutch connects up the one sprocket than when said clutch connects up the other sprocket.

13. Concrete pipe forming machine as claimed in claim 12, wherein the direction of rotation of the motor is reversible under the control of switchgear, the reversal of direction automatically actuating means for moving the clutch to change the gear ratio.

14. Concrete pipe forming machine as claimed in claim 13, wherein the means for moving the clutch comprises an arm driven by a friction drive from the lay shaft, which arm is coupled by linkage to the clutch.

15. Concrete pipe making machine comprising a supporting structure, a vertical supporting pillar substantially centrally of said structure, a carrier platform mounted to travel vertically on and supported by said structure, a vertical shaft mounted at its lower end for rotation on said carrier platform, a piston on the upper end of said shaft, retractable packer blade elements on said piston, an electric motor mounted on said carrier platform and coupled to the shaft for the rotation thereof, means for moving the carrier platform vertically on the supporting pillar, means for supporting a mould in axial alignment with the shaft and piston assembly, said means comprising mould locating and retaining members on a horizontal floor plate for the bottom of the mould, and mould locating and retaining members carried by a horizontal tray for the top of the mould, which tray is mounted on the supporting framework by means allowing for the raising and lowering thereof, means for maintaining the packer blade elements protuberant of the piston wall when said piston assembly travels upwardlyfrom the bottom of said mould for pipe formation, means for retracting said blades to within the piston diameter after pipe formation} the means for moving the carrier to return the piston after pipe forming operating to return said piston at a faster axial speed than during pipe formation.

16. Concrete pipe forming machine as claimed in claim 15, wherein the tray is mounted on a linkage connected to a counterbalanced operating ziaaagwo arm, said linkagybeing-a constnucted so that the m'ay 'will'in iovefverticaillyz 117; Concrete? pipea'formingimacmne': as claimed in: clainm- 16, whereinz amljusteflg1P!- stops are: provmeu tomaintainthe trayaga'inst 'upwardmovement during pipe-forming; operations, said. stops Iz.-bing; mounted and: connected; to: an operating ,ilever. whereby they may: be=SWH11gJ autwof. positionrto allow thetray: to rise:

NELSON: E. GOWING'.

REFERENCES The' fbllowing refrences are of record? in the 516- of 'this patent? UNITED, STATES PATENTS Number 

